The present invention relates generally to roofs, and more particularly to ventilators of the kind which are mounted in a roof and lie in the general plane thereof in place of one or more roofing elements, such as tiles, shingles or slates.
As is known, such ventilators are usually employed to ensure the ventilation of the space subjacent the roof to overcome the consequences of the inevitable condensation due to the difference between the interior temperature and the exterior temperature. Failing such ventilation, rapid deterioration, by rotting, of the frame or structural work and of the conventional insulation usually associated with the frame, is to be feared. The prior protective impregnation of the frame, in addition, reduces the effectiveness of such insulation.
Such ventilators may be employed in combination with suitable ducting to ventilate rooms of lower floors of the associated building and/or to exhaust fumes or foul air originating in such rooms.
Generally such ventilators comprise an opening for the desired flow of air. To prevent the entrance of foreign matter such as dead leaves or animals, it is common to at least partially close off the opening with an apertured panel, screen or grating. Most often the panel lies vertically so that the ventilator which extends at an angle relative to the panel to avoid direct admission of rain or snow for example, causes the panel to protrude substantially outwardly beyond the general plane of the roof to the detriment of the overall harmony of the roof.
In U.S. Pat. No. 2,973,704, however, it was proposed to arrange the apertured panel in the very plane of the roof. But to avoid or at least reduce the direct admission of rain or snow and to overcome the consequences of the entrance of the same, two related features were adopted.
According to a first feature the apertured panel comprised a plurality of inclined louvers. The second feature consists in leaving a passage of reduced cross-sectional area at the lower or downstream part of the opening and to arrange in the subjacent space and in continuity with the opening, a duct having a bottom wall which at least at its lower or downstream end is inclined toward the lower transverse edge of the opening and joined thereto so that all moisture, rain or snow, which enters through the opening is collected by the duct and carried back to the roof.
In the foregoing U.S. Pat. No. 2,973,704, the louver openings angle outwardly and upwardly with the exception of the lowermost louver opening which angles outwardly and downwardly to exhaust any moisture collected by the duct.
This arrangement is satisfactory in the absence of wind. Such is not the case when there are windy conditions and all the more so when winds are high.
In such cases the admission of snow or rain may be observed through the louver opening at the bottom of the panel when the wind produces an induced current of air which rises along the roof and through the other louver openings in the panel when the induced current of air flows downwards along the roof. A sufficiently large amount of precipitation may collect in the duct to cause the moisture to gain the subjacent space below the roof without it being possible to exhaust the same.
To reduce this drawback U.S. Pat. No. 2,973,704 provides deflectors or baffles above the uppermost louver and below the lowermost louver. The effectiveness of such deflectors or baffles is uncertain. Further, as these deflectors or baffles are separate parts from the rest of the panel their mounting complicates and increases the cost of installation of such a ventilator.